The present invention relates to spring-cushioned measuring resistors, which are embedded within a bushing in a ceramic casting. In particular, the invention relates to a turbocharger overheating protection device for preventing overheatings of the turbocharger of diesel engines whose turbocharger withstands a temperature range of −50 to +950° C., comprising a metal housing made of a mineral-insulated cable (also referred to as MIL), a receptacle and a sleeve projecting partly over each of the mineral-insulated cable and the receptacle, wherein a temperature measuring element is completely embedded in ceramic casting in the receptacle, the temperature measuring element is a measuring resistor or thermistor equipped with connecting wires, the connecting wires are connected by coil springs with the cores of the mineral-insulated cable. Furthermore, the invention relates to a method for manufacturing a turbocharger overheating protection device and its use.
A measuring resistor, in particular a film resistor or a thermistor, can be used as a temperature measuring element. A film resistor is a chip having connecting wires to thin film strip conductors on a substrate and a stress relief made of glass, which covers the connection region of the connecting wires and the strip conductor. Film resistors are known from the Heraeus brochure HSG-W2/D (April 1994).
German Democratic Republic Patent DD 72 602 teaches the cushioning of thermocouple wires by configuring them as coils. The arrangement of the elastic coils results in stress relief of the thermocouple wires and thereby prevents excessive mechanical stress, particularly breakages, which occur upon relative changes in length between the protection tube and the thermocouple wires clamped on both sides.
German Patent DE 10 2006 034 246 B3 discloses an offset bend in the connecting wire of the film resistor. The exposed connecting wires cannot withstand the high thermal and mechanical loads of turbochargers and break in the region of the offset bend.
German published patent application DE 10 2007 010 403 A1 discloses a construction suitable for turbochargers, in which the connecting wires are connected with one spring each, which is attached to the respective supply wire. The coil springs attached to the supply wires are stabilized by the supply lead as an axis and are used in the range of 900° C. to 1200° C.